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Thallium (Tl)

From Wikipedia, the free encyclopediaThallium is a chemical element with symbol Tl and atomic number 81. This soft gray post-transition metal is not found free in nature. When isolated, it resembles tin, but discolors when exposed to air.

Thallium in the periodic table

SymbolTl
Atomic number81
Group13
Period6
Blockp
Element categoryPost-Transition Metal

Physical properties

Phase at STPSolid
Density11.85 g/cm3
Atomic weight204.38 u
Melting point577 K
303.85 °C
578.93 °F
Boiling point1746 K
1472.85 °C
2683.13 °F

Atomic properties

Electronegativity (Pauling Scale)1.62
Electron affinity36.4 kJ/mol
Oxidation states−5, −2, −1, +1, +2, +3
(a mildly basic oxide)
Ionization energies
1589.4 kJ/mol
2 1971 kJ/mol
3 2878 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)[Xe] 4f14 5d10 6s2 6p1
Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p1
Electrons per shell2, 8, 18, 32, 18, 3

History

Discovered1861
Discovered byWilliam Crookes
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